Hi,
I used an instrument rack using a Hardware Instrument to send some midi data to my Volca Keys. Now I recorded the audio coming from the Keys to an Audio track for easier Mixdown, and would like to hide the original instrument track so it doesn't clutter my screen. I don't want to delete it, to be able to re-record it later if i make some changes.

Below your track lanes on the left navigation panel, there are six icons used to alter the way your arrangements are displayed. These are called, "Arranger View Toggles" :
The icon that looks like the letter X is the "Show/Hide Deactivated Tracks" toggle. Deactivate the tracks you're not using or don't want to see (to save CPU processing), then select this toggle to hide them. In my example, the tracks called Omni 7 & Omni 8 will become hidden when the toggle is selected because they've been Deactivated (they are shown as grayed out).

I suggest using this process to Deactivate all the tracks you aren't currently using in your Projects to optimize your CPU usage. In the basic set-up template I've created and use to begin my new Projects, all the tracks are disabled by default until I select one to use by Activating it - that way VST's and other FX devices inside the tracks aren't using up valuable resources.

For example, you can have track lanes set up with every VST Instrument you have, available and ready for use by simply Activating the track with (Alt/Option + A). This is the easiest way I've found to quickly audition several VST instruments - dragging a MIDI Clip from track to track, Deactivating the instruments I've decide to not use, then use the "Hide Deactivated Tracks" toggle option to clear away the clutter when I've found what I like.

Keep in mind that you can't choose individual tracks to hide. All Deactivated tracks will either be shown or hidden using the toggle. Also, there is also no current way (as of v 1.1.7) to hide an Active track.